The Geordie - who won promotion from the National League South three years ago - has been out of work since leaving Woking in March.
Dartford made their move after parting ways with Steve King following their failure to win the play-offs.
Dowson is now charged with taking the club up and will begin building a squad to attack promotion.
The Darts’ statement read: “We are delighted to announce that we have appointed Alan Dowson as our new manager.
“Dowse spent 7 successful years at Kingstonian, followed by 4 years at Hampton & Richmond Borough and Woking FC respectively.
“In his first season at Woking, they finished 2ndin the National league South and were promoted to the National League after beating Welling United in the Promotion Final.
“He brings a wealth of experience both as a player and a manager, Dowse will be naming his back room staff in due course.”